docs: 修掉「把没量的东西标成实测」的四处引用（M82 复审 P2）

- 两个 GUI main.rs：把「不 dlopen 任何图形库」改成「不依赖任何图形库（缺失时不影响）」，
  并把「实测见 §7」换成「§7.4 是依赖取证；耗时是结构性判断，没重量（§10-8）」
- packaging/README §1：§7.6（不存在）→ §7.4
- packaging/README §4：实测引用 §7.1 → §7.4（ELF 取证在 §7.4）
- packaging/README §7.4 标题补 ELF DT_NEEDED，并记下复审在 bookworm-slim 里的真跑结果
- packaging/release-notes：ull 示例前补 chmod +x（Release 资产不带可执行位）

packaging/release-notes.md

@@ -23,6 +23,7 @@ Every slot also ships the command line as its own small asset — `ull-{{VERSION
 (`.exe` on Windows):
 
 ```bash
+chmod +x ull-{{VERSION}}-linux-x64             # Release 资产不带可执行位，先补上
 ./ull-{{VERSION}}-linux-x64 instances list     # servers / CI / Termux: no graphics stack needed
 unlucky-launcher instances list                # desktops: the GUI binary answers the same commands
 ```